With the development of mobile communication, the demand for broadband access to a downlink such as a large capacity data transfer is increasing. HSDPA (High Speed Downlink Packet Access) is a protocol for such purposes, and the downlink transmission speed of HSDPA is improved to 12 Mbps, compared to 2 Mbps, the transmission speed of W-CDMA (Wideband-Code Division Multiple Access). The development of radio base station apparatuses and mobile terminals supporting HSDPA has increased in recent years.
As a technology corresponding to such an increase in downlink capacity, radio communication systems where an increase in uplink capacity is possible have gained attention, and EUDCH (Enhanced Uplink Dedicated Channel) has been discussed in 3GPP (3rd Generation Partnership Project). EUDCH can be described as an uplink version of HSDPA, and using an EUDCH control signal, a radio base station apparatus can control the data rate that a mobile station can transmit. By performing scheduling, an EUDCH enables a mobile station to transmit large data over the uplink. One of the major points in the discussion in 3GPP regarding the standardization of EUDCH is the handover between sectors (softer handover—SHO) with HSDPA, and what kind of technologies should be implemented in the standard has been debated.
The focus of the debate has been in which cell the scheduling of an EUDCH should be performed in order to realize the softer handover between the EUDCH and HSDPA. One method is to perform the scheduling of the EUDCH in the same cell as the serving cell (i.e. cell under service) for HSDPA. Another method is to perform the scheduling of the EUDCH in the other cell, which is different from the serving cell for HSDPA.
As a related technology, there is disclosed in Patent Document 1 a technology where an EUDCH service can be performed in an optimal radio environment although a UE (User Equipment) using the EUDCH service in a soft handover region receives different scheduling commands from a plurality of active Node Bs.
[Patent Document 1]
Japanese Patent Kokai Publication No. P2004-248300A
The description of this Document is incorporated herein by thereto.